1. Technical Field of the Invention
This invention most generally relates to automatic spray guns, both air atomizing and hydraulic pressure atomizing. In particular, it relates to automatic spray guns incorporating non-threaded couplings between all major body components and air and fluid supply lines.
2. Background Art
Conventional automatic spray guns in general have a shut off needle that seals on the back of a fluid tip or nozzle and an actuator to operate the needle with interference seals or packing to seal the liquid being sprayed. Conventional automatic spray guns also have threaded components such as a fluid tip or nozzle, threaded connections and a threaded packing retainer of some sort. Refer to prior art drawing FIG. 1, showing a conventional spray gun with a threaded air cap and threaded actuator cap, and threaded ports for inlet air and fluid line connections.
It has been standard procedure for many years in the food and pharmaceutical industries to use sanitary fittings wherever possible for valves, pipes, filters and other components, to meet both practical and regulatory sanitation requirements for avoiding contamination by or during the production process. Sanitary fittings generally consist of flanged joints having opposing flats that are abutted in a sealing fashion so as to minimize the potential for trapping trace amounts of the material in places that cannot be easily cleaned and inspected. The joints are secured for alignment and to hold against separation by pressure by mechanical means external to the seal.
In the past the use of threads has been allowed because of necessity. Automatic spray guns are complex fluid deposition nozzle mechanisms that have undergone considerable engineering scrutiny and development to optimize their performance for the many applications and fluids for which they are used. None the less, the use of internal threads has generally been considered an acceptable design solution for coupling aperatured components together for pressurized applications such as the body of the automatic spray gun. However, threaded pipe connections and couplings are inherently unsanitary. Internal threads in an automatic spray gun allow the ready accumulation and growth of bacteria, eventually contaminating the fluid flow. Threaded connections require frequent, time-consuming rotary disconnection and reconnection, and cannot be easily cleaned, polished, or inspected.
Some gun manufacturers have welded sanitary inlet connections to the body of the gun in an effort to provide sanitary connection ports for fluid and air line connections. In some cases the customer or user has undertaken to rework a standard spray gun model to gain this feature, because the sanitary inlet connection was not available from the manufacturer. This still does not address the problem of the threads that hold the fluid tip in place and also the threads that hold the seal retainer in place.
Readers may find UK Patent GB2199288 and U.S. Pat. Nos. 5,379,938, 4,348,040, 4,537,355, and 5,944,259, to provide useful context for a better appreciation of the invention, a description of which follows.
It is an object of the invention to eliminate or to isolate with seals the prior art threaded couplings common to automatic spray guns. It is a further object to improve the sanitary aspects of an automatic spray gun regarding use and maintenance, by eliminating threaded connections from the component parts. It is a yet further object to reduce the risk of contamination in the spray dispensing of fluids from automatic spray guns. It is a still yet further object of the invention to provide a face to face coupling between a nozzle body and fluid tip in a spray gun, that accommodates and seals axial and multiple annular passageways.
To these ends, in accordance with the invention, there is an automatic spray gun incorporating threadless, sanitary connection couplings for all air and fluid flow path connections. The spray gun nozzle body has threadless inlet couplings for air and fluid supply lines. The gun also has a threadless connection coupling between the fluid tip and the nozzle body and between the air cap and the fluid tip. The nozzle body/fluid tip coupling incorporates and seals, in some embodiments, multiple passageways for air and fluid flow such as a center passageway for fluid flow plus annular middle and outer passageways for atomizing air and fan air respectively.
The nozzle body also has a sanitary connection for the needle actuator on the back end of the gun. The actuator can be a conventional mechanism or a diaphragm sealed shut-off/clean out needle mechanism or such other mechanism as may be available. The actuator may be omitted and the position closed off with a threadless connection cap in applications where air and fluid flow are controlled externally. Limited departures from the all-sanitary connection couplings model can include threaded cap couplings for attaching the air cap and/or the actuator body, where the application requires accommodation of components still utilizing threaded connections.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein I have shown and described only a preferred embodiment of the invention, simply by way of illustration of the best mode contemplated by me on carrying out my invention.